The most straightforward delay analysis compares the programme as it stood at the start with the sequence actually achieved. It is cheap, it is easy to follow, and on projects with ordinary records it is frequently the only method available, which is why it comes up early in extension of time claim preparation.
Its weakness is that it shows what happened without showing why, so the causal work still has to be done. Its strength is that everyone can read it.
What the comparison does
It sets the planned start and finish of each activity against the actual start and finish, so that slippage is visible activity by activity and period by period.
Where the slippage accumulates along a chain, the delay to completion follows from the comparison rather than from any calculation.
Presented on a single sheet, it gives the reader the shape of the project in under a minute, which no other method does.
What it does not do
It does not identify cause. An activity that started late may have been delayed by an employer risk event, by a subcontractor, or by a decision to sequence the work differently.
It does not account for changes in the governing chain, since it compares against one baseline throughout.
And it does not distinguish delay that affected completion from delay that was absorbed by slack, which is the distinction the claim depends on.
What it needs to be credible
A baseline programme that was actually in use at the start, submitted or accepted under the contract where the contract requires it.
Actual dates taken from contemporaneous records rather than from recollection: progress reports, valuations, site records, subcontractor accounts.
And a consistent activity list, so that the comparison is between the same activities rather than between two different views of the work.
Adding the events
The comparison becomes an analysis when the events relied on are placed on it by date, so the reader can see what arose immediately before each slippage.
That is not proof of cause and it is a strong indication, particularly where the sequence of event and effect repeats across the project.
Where an activity slipped with no event anywhere near it, the comparison shows that too, which is worth knowing before the other side points it out.
Windows
Dividing the project into periods, and looking at what governed completion within each, addresses the main weakness of the method at modest extra cost.
Each window has its own governing chain, its own events and its own slippage, which is much closer to how the project actually behaved.
The windows should follow the project rather than the calendar: a change in what was driving the work is a better boundary than a quarter end.
Where the baseline is poor
A programme with no logic can still support the comparison, since the comparison itself does not need logic, only dates.
What it cannot then support is any statement about which chain governed, which limits the claim to what the dates themselves show.
Saying that plainly is better than implying an analysis the programme cannot carry, because the limitation is obvious to anyone who looks at the programme.
Where no baseline exists at all
Sometimes the only programme is one produced months into the works, which is not a baseline and should not be presented as one.
A tender programme, or a sequence reconstructed from the contract documents and the information release schedule, is sometimes the honest starting point.
Either way it should be identified for what it is, because a reconstructed baseline presented as contemporaneous is the kind of thing that costs a claim its credibility entirely.
How the other side attacks it
By pointing at the absence of cause, which is fair, and which is why the events and records have to accompany the comparison.
By arguing that the baseline was unachievable, which is why a baseline built from resources and output matters.
And by identifying contractor delays visible on the same sheet, which is why dealing with those openly is better than waiting to be asked.
When it is enough
On projects where the cause of delay is plain, where the events are few and well documented, and where the sums do not justify a larger exercise.
That describes a great many projects, and a proportionate analysis settles them where a disproportionate one would still be in correspondence.
The test is whether the reader can follow the claim without instructing anybody, and this method usually passes it.
When something more is needed
Where there are many events, overlapping effects, and a real dispute about which chain governed at different times.
Where the sums at stake justify the cost, and where proceedings are likely rather than possible.
Detailed delay analysis is a specialist field, and where a dispute genuinely needs it, saying so is better than offering an approximation of it.
Presenting it
One sheet with the comparison, the events marked by date, and the slippage along the governing chain highlighted.
A short narrative that walks through the periods, referring to the records rather than reproducing them.
And a clear statement of what the method shows and what it does not, which takes a paragraph and buys a great deal of goodwill.
Preparing it from ordinary records
Progress reports, valuation records, site diaries and subcontractor accounts between them usually establish actual dates to within a week, which is sufficient for most purposes.
The work is in reconciling them rather than in any analysis, and it is ordinary surveying work rather than anything specialised.
Which is why this method is available on projects where nothing more sophisticated is, and why it is worth doing properly rather than quickly.
Where it fits
The comparison establishes what happened, which is the foundation for the entitlement argument rather than a substitute for it.
Whether the events relied on carry relief under the contract is initial dispute review work, and it runs alongside the comparison rather than after it.
The records that make the comparison possible come from ordinary cost control and variations during the works, which is why well administered projects produce this analysis in days.
Running late with nobody agreeing why?
Extension of time claim preparation sets out the events relied on, their effect on the programme and the contractual route to relief, in a form that can be assessed rather than argued over.